Simple chemical modifications to oligonucleotide ends with hexaethylene glycol and hexanediol are shown to significantly increase nuclease resistance under serum conditions. The modified oligonucleotides were used to construct DNA prismatic cages in a single step and in quantitative yield. These cages further stabilize their strands towards nucleases, with lifetimes of 62 hours in serum. The cages contain a large number of single-stranded regions for functionalization, illustrating their versatility for biological applications.